2,8-dihydroxydibenzothiophene



Patented Oct. 16, 195i 2,8-DIHYDROXYDIBENZOTHIOPHENE Frederick P. Richter and Everett W. Fuller, Woodbury, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Original application .April 5, 1947,

Serial No. 739,650. Divided and this application December 22, 1948, Serial No. 66,827

1 Claim.

This invention relates to a method for the preparation of poly-hydroxydibenzothiophenes and alkyl-substituted monoandpoly-hydroxydibenzothiophenes and the products so prepared.

Prior to this invention, 2-hydroxydibenzothiophene and its preparation were described in German Patent 606,350, Example '2, November 30, 1934. Insofar as is known, no method has been previously disclosed for the manufacture of any other monoor poly-hydroxydibenzothiophene, nor has any method been disclosed for the preparation of alkyl-substituted mon-oand polyhydroxydibenzothiophenes. Therefore,.of course, the compounds themselves have not been previously disclosed.

According to this invention, it has been discovered that dibenzothiophene can be halogenated by means of chlorine or bromine with or without a-catalyst, to produce di- .or poly-halogenated dibenzothiopheneand.the.halogenated.dibenzothiopheneso produced can be hydrolyzed by treating it withan alkali .oralkaline earth hydroxide such as barium hydroxide octahydrate, and thereafter acidifying with a mineralacid. Suitable-catalysts such as .copperor copper-bronze powder may be used to aid inthe reaction of the hydroxide with .the halogenated product. The :result is a .dior -poly-hydroxydibenzothiophene.

It :has further beendiscovered that themonohydroxydibenzothiophene, and also .dior 11013- hydroxydibenzothiophene produced as mentioned hereinbefore canbe alkylatedfor. example, by reacting them with an anhydrous alcohol in the presence of an anhydrous metal halide, such as zincchloride, orby subjecting them toiaFriedel- Craftstype of reaction with. an alkylhalidei-nthe presence of a catalystsuch as aluminum chloride :or 110mm .trifiuoride.

'Still-furthenithasbeendiscovered,thatmonoe, di- .and pclyehydroxydibenzothiophones and the :alkyl-substituted;mono-=, diand poly hydroxydibenzothiophenes will all act, whenincorporated .in lubricating compositions, to inhibit.deterior a- 'tion and the tendency to oxidize of the lubricating compositions.

REACTANTS start with an already halogenated dibenzothiophene.

It appears'that when only one hydrogen-ineach molecule of dibenzothiophene is replaced by the halogen, the halogen is usually inserted in the 2.-

position, and that when two hydrogens are re:- placed by halogens, that the halogens are usually inserted in the 2- and 8-positi0ns. Therefore, 2 halodi-benzothiophene and 2,8-dihalodibenzothiophene may be considered to be preferred examples of compounds formed by the first reaction in the process, or as compounds with which to begin the preparation of the compositions of this invention.

Barium hydroxide octahydrate may be considered as a preferred example of an alkali or alkaline earth hydroxide with which to convert the halodibenzothiophene into an hydroxydibenzothiophene. Any alkali or alkaline earth hydroxide will perform this function. Other examples of such bases are sodium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, etc.

Copper powder may be considered as a preferred example of a catalyst which may be used to assist in thereaction of the hydroxide with the halodibenzothiophene. Any other similarly acting catalyst, such as copper-bronze powder, silver powder, precipitated copper, electrolytic copp r, etc may be used for this purpose.

If the hydroxydibenzothiophene is to be alkylated, this may be accomplished by the use of an aliphatic alcohol, preferably a tertiary alcohol. Tertiary amyl alcohol may be considered to be a preferred example. Cycloaliphatic alcohols and aliphatic alcohols having other than aliphatic substituents may also be used.

Halides corresponding to the alcohols mentioned above, olefins, and other compounds that contain'an alkyl chain and will condense with aromatics to alkylate them may be used in place of the alcohols described above.

The alkylation may be catalyzed by anhydrous zinc chloride, which has-been found preferable, or by any other alkylation catalyst. Aluminum chloride, boron trifiuoride and hydrogen fluoride are examples of such catalysts.

REACTION CONDITIONS The halogenation of the dibenzothiophene may be accomplished by subjecting the dibenzothiophene to the desired halogen in an amount sufficient to halogenate the dibenzothiophene to the desired extent, at temperatures ranging from "about- C. to about 300 C. and at-pressures ranging'from'atmospheric to about 100 pounds, per square inch. It is preferable, although not -necessary,to carry out the halogenation in the presence of a catalyst, such asiron powder. E-xcess halogen'may be blown out by an inert gas after thereaction has completed itself, or distilledoif from-the final product.

. 3 The halodibenzothiophene is converted into hydroxydibenzothiophene by treatment with the hydroxide, preferably, but not necessarily, in the presence of a catalyst, usually in the presence of an excess of water and usually at an elevated temperature. By utilizing pressure to prevent the vaporization of water, a temperature of about 220-275 C., and preferably a temperature ofabout 240-260 C., can be used, at which terr 1- perature the reaction will complete itself in 24 hours or less when using barium hydroxide octahydrate and copper powder.

In general, it is preferred to use an excess of the hydroxide over the amount theoretically required. This excess may be from 1 to 5 times the amount theoretically required. Preferably also, an amount of catalyst equal to about 3 to 6% of the total charge will be used, although the reaction can be accomplished in the complete absence of a catalyst, if desired.

Barium hydroxide octahydrate is preferred because it causes no carbonization, and copper or copper-bronze powder is preferred as a catalyst. The reaction may be accomplished either with or without agitation.

The resulting solution is preferably filtered and the filtrate acidified with a dilute mineral acid, such as hydrochloric acid, to liberate the hydroxy derivative. The crude product so produced may then be crystallized from dilute alcohol to purify it.

In order to obtain the alkylated product, the mono-, dior poly-hydroxydibenzothiophene may be reacted with a sufiicient quantity of anhydrous alcohol in the presence of an anhydrous v:

alkylation catalyst such as zinc chloride. This is preferably accomplished by stirring the reactants and catalyst together at a temperature ranging from about 165 C. to about 185 C. for from about 6 to about 10 hours in the presence of anhydrous (fused) zinc chloride in a ratio of 1.25 to 4 times the amount of hydroxydibenzothiophene used. It is desirable, although not strictly essential, to distill off and trap the water formed in the reaction. At least one mole of alcohol should be employed per mole of hydroxydibenzothiophene and if higher allrylation products are desired, ratios up to about 2.5 moles of alcohol may be employed per mole of hydroxydibenzothiophene. Higher ratios are not recommended for use at atmospheric pressure since it then becomes difficult to operate in the preferred temperature range. Thereafter, the product is freed from the catalyst and other watersoluble impurities by dissolving it in benzene or an equivalent organic solvent, washing with water, drying and removing the solvent by distillation.

OIL BASE The hydroxydibenzothiophenes and alkylated hydroxydibenzothiophenes described above have been found particularly useful as ingredients in lubricating compositions, where they materially reduce the tendency of the composition to deteriorate and oxidize.

These materials may be incorporated in any which may be added for the purpose of effecting the same improvement or other improvements in that composition.

Ordinarily, the new composition described above will be added to lubricating compositions in amounts ranging from 0.01% or less to 1.0% but may be added in amounts up to 10%, in some instances. Those of the new products that are sufliciently soluble in oil may be marketed in the form of oil concentrates in which the per cent of the new products is greatly in excess of that which is desired in the final lubricating composition, for example, quantities up to by weight.

Further details and advantages of this invention will be apparent from a consideration of the following specific examples and results of tests.

EXAMPLE I (2,8 -dihydroscydibenzothiophene) A mixture of Parts 2,8-dibromodibenzothiophene 25.7 Barium hydroxide octahydrate 94.5 Copper powder 15.0

Water 175.0

was heated under pressure at 240 C. to 260 C. for 24 hours. The reaction product was extracted several times with boiling water, the solution filtered and the filtrate acidified with dilute hydrochloric acid. The precipitated crude 2,8-dihydroxydibenzothiophene was crystallized from dilute ethanol and yielded 13.2 parts (82% yield) of a white crystalline product. A portion recrystallized from dilute methanol melted at 278 C. to 279 C. (uncorr.). It was found to contain 14.76% sulfur. The calculated percentage of sulfur for 2,8-dihydroxydibenzothiophene is 14.83%.

A saturated oil solution of 2,8-dihyclroxydibenzothiophene was prepared using as the oil a highly refined mineral oil suitable for use in transformers and prepared by treating a Coastal distillate with 40 lbs. of 93% sulfuric acid and 180 lbs. of 103% oleum per barrel followed by washing and clay percolation. This oil had the following physical properties: specific gravity 0.871, flash point 310 F., Saybolt Universal viscosity sec. at 100 F. It is characteristic of this type of oil to produce acidic products on oxidation. The blank oil and the oil containing 2,8-dihydroxydibenzothiophene dissolved therein were tested by heating the samples at 120 C. and bubbling oxygen through the heated oil for a period lubricating composition ranging from gasoline of 70 hours. The acids thus formed were titrated with alcoholic potassium hydroxide, the results being expressed as the neutralization number which represents the number of milligrams of potassium hydroxide required to neutralize the acidic bodies contained in one gram of the test oil. That the dihydroxydibenzothiophene materially improves the stability of the petroleum oil toward oxidation at an elevated temperature is shown by the following data:

After 70 hours N. N. Blank oil 20.0

The same oil saturated with 2,8-dihydroxydibenzothiophene, the amount dissolved being less than 0.01% 6.7

The oil blend did not contain suspended dihydroxydibenzothiophenesince it was carefully filtered through a filtering clay prior to testing.

EXAMPLE II Parts 2-hydroxydibenzothiophene (M. P. 159 C.) 100 Anhydrous tertiary amyl alcohol 44.1

Anhydrous (fused) zinc chloride 136.3

The 2-hydroxydibenzothiophene and zinc chloride were placed in a reaction vessel which was equipped with a mechanical stirrer, water cooled condenser and thermometer dipping into the liquid. The tertiary amyl alcohol was added rapidly with constant stirring and the temperature was raised to 180 C. and held at 175-185 C. until the reaction was complete, about 6 hours. The product was freed of zinc chloride and other water soluble impurities by dissolving the crude material in benzene, washing with water, drying and removing the benzene by distillation under vacuum. The residue consisting of alkylated 2-hydroxydibenzothiophene could not be readily recrystallized from a solvent because it contained isomeric tertiary amyl derivatives. The identity was established, however, by analysis. Calculated for Cl'IH180'sIs=11.9%; Found: S=12.2%. Calculated for CrzI-ImStOH) Hydroxyl number-=207. Found: Hydroxyl number=223.

The tertiary amyl hydroxydibenzothiophene prepared above was found to be considerably more soluble in petroleum oils than the 2-hydroxydibenzothiophene from which it was prepared. An 0.5% solution in the test oil described in Example I was prepared and tested according to the method described in Example I. The neutralization number of the treated oil at the end of the test was only 0.02 mg. KOH/g. of oil indicating that the tertiary amyl hydroxydibenzothiophene had greatly stabilized the oil toward oxidation. Further tests were made in order to evaluate the oxidation inhibiting effect of the alkylated hydroxydibenzothiophene. The oils used in these tests were: (A) a moderately refined oil which was a mixed Mid-Continent and Coastal distillate which had been refined by treatment with '70 pounds of 98% sulfuric acid per barrel, neutralized, washed and percolated through clay. It had a specific gravity of 0.879, a flash point of 385 F. and a Saybolt Universal viscosity of 152 seconds at 100 F. It is an oil suitable for use in turbines. (B) a solvent-refined oil that consisted of a distillate from a Rodessa crude which had been refined with furfural, dewaxed, and filtered. It had a specific gravity of 0.846, a flash point of 420 F. and a Saybolt Universal viscosity of 151 seconds at 100 F.

TEST I The test involved maintaining a cc. sample of the oil or oil blend at a temperature of 200 with 5 liters of air per hour bubbling therethrough. Each sample contained 24 inches of No. 18 gauge copper wire and one gram of iron granules and 2 cc. of distilled water were added each day. The samples were tested after varying intervals for acidity, color and sludge, and the results for the blank oil and the blends containing the additive are as follows:

Test Sample Time Color I N. N. Sludge 0.2% tertiary amyl hydroxydibenzothiophene in Oil A.-- 0.2% tertiary amyl hydroxydibenzothiophene in Oil A on A uninhibited H ours Mg.

TEST II The oil used in this test was a solvent-refined S. A. E. 20 grade motor oil which is normally corrosive to bearing metals having the corrosionsusceptibility of cadmium-silver alloys. The oil was tested by placing a section of a bearing containing a cadmium-silver alloy surface and weighing about 6 g. in a sample of the oil or oil blend and heating the oil sample to a temperature of C. for a period of 22 hours while bubbling a stream of air therethrough against the surface of the bearing. The loss in weight of the hearing as a result of this treatment measures the amount of corrosion that has taken place. A sample of the oil containing the addition agent is run simultaneously with a blank and the loss in weight of the bearing section in the inhibited oil can thus be compared directly with the loss in weight of the bearing section in the blank. The results are as follows:

Loss in Milligrams Test Sample 1% tgtc-lamylhydroxydibenzothiophene in the oil descrl e 0.5% tert-amylhydroxydibenzothiophene in the oil described Blank oil zero 22 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,479,513 Richter Aug. 16, 1949 2,499,186 Flowers Feb. 28, 1950 2,509,938 Patterson May 30, 1950 FOREIGN PATENTS Number Country Date 768,052 France May 7, 1934 296,761 Great Britain Aug. 1, 1929 

